Abstract P1016: Modeling Ventricular Hypoplasia In Pulmonary Atresia With Intact Ventricular Septum Using Patient-Specific Induced Pluripotent Stem Cells

Pulmonary atresia with intact ventricular septum (PA-IVS) is a detrimental congenital heart disease where the pulmonary valve is not appropriately developed. Several hypotheses speculated to explain the pathogenesis of this disorder contains abnormal coronary arterial development, atypical blood flow through venous valve and atretic pulmonary valve formation. Conventional treatment strategy is pulmonary valve perforation, and PA-IVS patients after treatment present with varying degrees of ventricular hypoplasia: from single ventricle palliation (1v) to 1½-ventricle palliation (1.5v) and bi-ventricle repair (2v). Mechanistic studies are required to further explain the different levels of RV hypoplasia in PA-IVS patients. Here, we generated PA-IVS-specific induced pluripotent stem cells (iPSCs) from patients with a spectrum of RV hypoplasia. PA-IVS iPSC-derived cardiomyocytes (iPSC-CMs) contracted normally and displayed sarcomeric structures with intercalated cardiac troponin T and α-actinin. Early-stage PA-IVS iPSC-CMs exhibited a variety of compromised proliferation activities, which were not able to be rescued by Wnt signaling pathway activation. Transcriptomic profiling by bulk RNA seq suggested that pathways involved in the cell cycle and mitosis were downregulated in day13 PA-IVS-1v iPSC-CMs, but not in PA-IVS-2v iPSC-CMs. However, at later stage (day20), pathways involved in the regulation of cell division and mitosis was upregulated in PA-IVS-1v cardiomyocytes, indicating a possible developmental delay in the cardiomyocyte proliferation for PA-IVS-1v. Intriguingly, differentially expressed genes between PA-IVS-2v and control CMs were mostly enriched in the pathways relevant to glucose metabolism, mitochondrial biogenesis, and muscle contraction. The differentially involved pathways between PA-IVS-1v and PA-IVS-2v cardiomyocytes suggest that an intrinsic transcriptional program may lead to divergent degrees of cardiomyocyte proliferation and ventricular growth in PA-IVS. We conclude that patient iPSC-CMs can recapitulate cardiomyocyte proliferation defects which are involved in ventricular hypoplasia in PA-IVS.